THE BOOK OF MIGRATORY BIRDS 85 



remarks, its eyes seem to be peculiarly calculated for 

 collecting the faint rays of light in the darkened vales and 

 sequestered woodlands during nocturnal excursions, thus 

 enabling it to avoid trees and other obstacles. It is 

 probable, indeed, that the proverbial stupidity of the bird 

 arises from this weakness of sight. Like the owl, indeed, 

 its motions are much more agile and lively at nightfall and 

 dawn than at any other time; and so strong is this pro- 

 pensity to action at the rise or descent of the sun that 

 woodcock when kept in a room are observed to flutter 

 about regularly every morning and evening, while 

 during the day they only trip on the floor without 

 attempting to fly. 



The stone-curlew differs from the last-named particu- 

 larly in this, that, though its eyes are similarly prominent, 

 its sight is very acute in the daytime. The prominence of 

 its eyes enables it to see behind as well as before, and it 

 is with difficulty, therefore, that it can be approached. 

 With respect to owls, as well as night-prowling animals, 

 the eye is unquestionably very sensitive. 



Of the barred owl an experienced naturalist remarks, 

 "Its power of sight during the day seems to be rather of 

 an equivocal character, as I once saw one alight on the 

 back of a cow, which it left so suddenly afterwards, when 

 the cow moved, as to prove to me that it had mistaken the 

 object on which it had perched for something else. At 

 other times I have observed that the approach of the grey 

 squirrel intimidated them, if one of these animals acci- 

 dentally jumped on a branch close to them, although the 

 owl destroys a number of them during twilight." 



Wilson says of the snowy owl that "the conformation 

 of the eye forms a curious and interesting subject to the 

 young anatomist. The globe of the eye is immoveably 

 fixed in its socket by a strong, elastic, hard, cartilaginous 

 case, in the form of a truncated cone. This case, being 

 closely covered with a skin, appears at first to be of one 

 continued piece, but on removing the exterior membrane 



